One of the main "selling" points for a quilt is that for an equal amount of TOP layer loft, one can save weight by using a quilt instead of a bag because there is no bottom, hood or zipper etc. Other items you already carry can be used to take care of the bottom and hood etc.

While perusing Nunatak's site, I was comparing the Arc Bag and the Arc Quilt, both rated at 20* with 2.5" baffles, in size Medium with a Quantum shell.

One is a bag with short zipper the other a quilt, both with equal top layer loft.

What struck me was that the BAG is only 1.0oz heavier than the QUILT! BUT the bag has 0.5oz more fill, making it only 0.5oz heavier when taking this into consideration. Furthermore the bag has wider dimensions. Given equal dimensions, they may be exactly equal in weight.

WOW! A bag with equal top layer loft and fill, that weighs the same as a quilt! Can this be possible? Especially since the bag has a hood, a bottom and a short zipper.

Now I know Nunatak's weights and specs are not exact since they are mainly a custom shop, but if the specs are on, this is one case where a bag is equal to a quilt in loft and weight and to me that is major news.

Perhaps this post should have been an email to Tom first for clarification, but I thought it was too cool not to post here first and see what it stirs up.

I'm just speaking in terms of weight and loft here, not considering any of the other reasons one might choose a quilt or bag.

But, given equal weight and top layer loft…there would a ruckus amongst us with the quilt users wondering if now a quilt is really the best choice. Of course, when one factors in the other reasons for choosing a quilt it may not be that big of a deal.

I also notice the medium bag fits to 6' while the quilt fits to 5'10". I would think that even with the 1/2 oz more down & the same height baffles, the loft would have to be slightly less in the bag than the quilt.

Just guessing, but maybe the quilt just has a somewhat higher temperature rating for the amount of loft due to factoring in for some loss of heat around the sides when moving? And the bag actually could have slightly less loft but be rated as warmly due to less anticipated heat loss due to the more complete enclosure?

Definitely worth emailing Tom. It may be a difference in construction, ie a quilt is not likely to be cut differentially (unless you make a special request), but the mummy is likely to have a differential cut which might make the down more efficient in loft:weight. The extra straps on the quilt may negate the weight difference of the zipper on the bag.

Other than that, I doubt the quilt would be the same warmth as the bag UNLESS you paired it with a decent down hood/hat. This is from personal experience. So I would add the weight of a down hood to the total weight equation of a quilt if you really want to push it to 20 degrees. The only advantage I see with a quilt is for folks who sleep hot and want to easily be able to stick their feet out or sprawl. Or sometimes side sleepers like to wear their hood separately so they don't suffocate and the hood satys with them when they roll over. We also use an extra wide "quilt" when theres two of us and the weather looks OK.

The website SAYS the bag has 2.5 inch baffles. This implies that it should be that thickness all around, including the bottom. I don't know if the bag has side baffles to stop the down from moving around, but if it doesn't you could potentially shake more of the down to the top of the bag. I used to do this with my WM Ultralite and it definitely increased the warmth.

I still think we should wait to hear from Tom before we decide that top bags are less weight efficient than mummy bags…The quilt has less area to fill, but almost the same amount of fill as the bag, so maybe the density is higher/warmer (over-filled baffles)?

I noticed that fill weights for both the bag and the quilt are about the same (11.5 vs 11 oz in size M). This means that there is 11 oz in the quilt (only a top layer) vs 11.5 oz spread around the top and bottom layers in the bag. This should result in much greater loft for the quilt. Considering both the quilt and bag have 2.5" baffles, maybe the quilt is overstuffed?? It seems hard to believe that a generously sized bag with the same amount of fill as a smaller quilt (fill spread through only one layer) would provide the same warmth. Maybe I am missing something?

I emailed Tom from Nunatak and asked him if he could comment on our discussion here, he replied and asked me to post this for him at BPL since he is very busy right now making great custom gear! I have added editorial remarks between brackets [] where I am not clear exactly on what he means or just to clarify:

=== Begin Tom's Response ===

Yes, the weight charts are close, and with similar fill weights we accomplish very different objectives to attain a warm setup.

On quilts, were wanting a fully lofted blanket over and on the side of you. With the Alpinist [bag], we are relying somewhat on the bag effect for greater warmth.

True, the top and sides of the bag are both 2.5" and should be fully lofted, materials are allocated differently with a hood setup.

With Alpinist [bag] stock fill, you can loft the top and sides to the max, but the entire surface area is not lofted fully, and about half of that is under you in a mummy shape. And so with continuous baffles you can adjust fill to regulate warmth right? A little overfill is nice with any gear. However, with an Alpinist [bag?], you can jump total loft from 2.5-3" to 5" with another 4 ounces [from the bottom?].

Also, in a mummy shape, the down is under greater pressure from the effect of the two concentric circles the shells form around it. Thus you can use a little less [fill?] than you might anticipate and achieve the same loft.

Whereas the quilt is setup to be more useable like a blanket, with maximum loft when sides are tucked under you.

I hope to this helps and makes sense!

=== End Tom's Response ===

So, if I understand correctly, the bag uses equal down to fill more space, and achieve the same temp rating and weight, because of the way the bag wraps around one (tighter concentric circles as Tom put it and the "bag effect".

Speaking in terms of warmth and weight the bag seems the winner hands down. What exactly is the advantage of the quilt (again speaking only in terms of warmth to weight ratios)? I realize quilts have advantages with versatility etc, but taking this narrow line of thought and focusing on warmth to weight is educational.

I don't follow the conclusion that, judging weight/warmth, a bag is superior to a quilt as a general proposition.

Afer all, with a bag, there is always some amount (weight) of shell, liner, and insulation squashed under your body, providing no warmth beyond helping to block drafts. But all that extra material and insulation is not flattened underneath you when using a quilt, so deduct that wasted weight and add it in the quilt's top to do some good.

And realistically, variables would seem to play a great role in the performance of either a quilt or a bag. A bag may be better than a quilt under one set of circumstances, but not as good under different circumstances.

For example, at least to me, quilts rule when using a tarp with bivy. The bivy greatly helps eliminate drafts, and also helps retain warmth for the quilt.

If weight/warmth of a quilt used with a bivy is to judged with the weight of the bivy, too, then a bivy's weight would also have to be counted as part of the weight for the bag option. Unless, of course, the bag has a shell that's sufficiently water-resistant to do without added protection of a bivy. But, then, there'll be the added weight of a heavier shell on the bag to provide needed protection, with perhaps diminished breathability for the bag — unless the bag has an eVent shell that can be said to breath as well as a Quantum shell on a quilt.

I wouldn't consider the weight of separate head insulation to be part of the quilt's weight since I would have that head insulation packed as part of my gear anyway — one or more of the following: balaclava, fleece beanie and/or hood on an insulated jacket.

Even if all else were equal (bivy or not, tarp or tent, an individual's unique metabolism, weather, etc.), it appears to me that the quality of design and materials for one particular quilt or bag can make a huge difference when comparing weight/warmth — so that generic comparisons of "bags" to "quilts" is difficult, if not impossible.

The adage "apples to oranges" comes to mind.

As a practical matter, aside from warmth to weight ratios, I find it much easier to get into a bivy when using a quilt, as opposed to the bivy/sleeping bag combination.

With the above, and the fine work by Tom at Nunatak, I believe my Arc Alpinist serves my needs very well, both for warmth and weight. My Arc weighs 24 oz, a few ounces greater than the stock version because I chose to have differential cut between the shell and liner to allow unrestrained lofting, and also chose 3" baffles rather than 2 1/2" to accomodate even more lofting with the 2 extra ounces of down also added. The long stock version would have been too long, and the medium would have been too short — so I had it sized in between medium & long.

No understatement to say: It's a great quilt, and I'd pick it instead of a bag everytime — unless synthetic is called for because of conditions. Then I'd take a quilt with synthetic insulation.

So, I need a new bag, and I think I'm going with a bag simply so I don't have to wear a stinkin hat all night. I mean, I already have to wear a hat all day to keep the scalp from burning, it seems it'd get old to have to wear a hat all night too.

I think Tom's quote "Yes, the weight charts are close, and with similar fill weights we accomplish very different objectives to attain a warm setup" is the bottom line. Some folks prefer quilts, others prefer mummy bags. All the specs and temerature theories in the world will not change that!

I also had a 3" differentially cut Arc Alpinist and couldn't get rid of it fast enough (thanks for the WM POD swap Pedro). But I would have never known I didn't like quilt style sleeping if I hadn't tried it for myself. Using a bivy to achieve the needed warmth with a quilt negated the benefits of not being constrained to a mummy shape, and the hat thing really sucks IMHO. But since there are plenty of people who would just about die to defend their quilts, I just shrug my shoulders and figure it's like everything else in life. I definitely would add the weight of hat AND bivy bag to the weight of the quilt as I didn't carry either of these with a mummy bag. And even with bivy and hat I never felt as warm. Different strokes….

From Tom's reply, I glean (although it's not clear) that the bag style without side baffles allows the down to be shaken towards the top of the bag, making for greater potential loft on the top and sides where it counts. This is my experience as well (WM UltraLite is a great example of this that I've used this way), plus with a full side zip I can still use a mummy like a quilt with a foot box on warm nights or resltess sleeping, so the bag is win-win.

Nunatak quilts drape around the body almost all around as you can clearly see in the picture of the bottom side. This is good. It surrounds the sleeper with down still saving the contact points at the bottom but I guess this puts these quilts very close to bags in weight. Also consider the Alpinist bag has a short zip which many people don't like. It's not like the average bag. Still I find difficult to believe those figures because of the hood… and I wonder if there's an insulated envelope behind that zipper. If there isn't, I see a potential cold area and if there is, the less I understand the figures but anyway… weight savings, if any, are not really the big advantage of quilts.

Quilts are variable girth and that makes them super versatile. With a bag, you are strictly limited in how much clothes you can wear inside and if wearing no clothes you'll have some extra room that's working against you. You have to take a compromise. With a quilt, there's virtually no such compromise (to a degree… there's always limits) because you can use the quilt as snug as you need it to. This is a very important issue particularly in the long distance hikes or anytime there's a potential for a wide range of conditions in a trip. The absence of a hood is something I like, be it in a quilt or a bag. You can have a tight seal at neck level and then have whatever you use as a hood independent of the rest and moving with your head. In a mummy, if you turn you have to do it together with the bag or you'll be breathing inside your hood, which is a bad thing for your insulation. When you turn with your bag, you expose an area with crushed, unlofted insulation that will take a while and some energy off you to loft and warm up and if you shaked most down out of there then you're left with almost nothing.

With a bag, you're crashing some down under you every night. This is bad for your down but I don't know if it's any worse than compressing the bag for storage, which you also do every day anyway but it makes me feel bad. This may be more psychological than practical.

I've done many trips with a quilt where my hood at night was something I would have carried anyway (I was carrying it when I was using a mummy bag) so I don't think it's fair to say the hood weight is extrictly extra. Maybe part of it, it'll depend on the trip and the person but most of us carry some insulating hat regardless of sleeping bag choice.

About the bivy thing, I don't think it's so key to make a quilt work (at least for Nunatak quilts) but a bivy or bag cover will make many other things for you other than stopping drafts if you're using a quilt. A bivy or bag cover is standard equipment in many gear lists, also lightweight ones. I sometimes carry one and it'll depend on the rest of my kit but not particularly in the bag/quilt choice. One important thing here is no matter how waterproof a bag shell is, you'll push humidity in when you store the bag in the morning if there's any on the shell. It'll not always be possible to hang the bag to dry before storing. A bivy or bag cover will help a lot with this.

Bottom line, I think this bag/quilt choice is a very personal one, as is the long/short/no zipper or the girth in bags. Quilts have some advantages but they're worth nothing if you just don't sleep well in one. Also, very important, it depends a lot on the rest of your kit to make your sleep system work, be it based on a quilt or a bag. The weight difference, if any, is by far not the most important factor, IMO. We can't really say a quilt is better or worse than a bag, choose what works for you.

I had started a similar thread comparing bag vs bag and then quilt vs bag The flaw in my logic is that I was comparing quilts to bags of *equal* temperature ratings.

The weight differences between a 20 degree quilt vs a 20 degree bag are the *same*. Where the weight savings come into play is that you leverage your existing insulation to increase the bag rating. You can go crazy comparing manufacturer ratings of loft to loft, fill to fill, but it's not very scientific since the bags can vary.

Part of every 3 season gear list should be an insulation layer. A cocoon hoody will add a maximum 14 degrees of warmth. If you're already bringing a cocoon hoody, why not use it to boost the effectiveness of your sleeping system? So instead of packing a 32 degree bag that would weigh in at about 20 ounces [WM Summerlite states 19, but 20 is more accurate] *and* a cocoon hoody that would not be utilized, bring a 40 degree quilt [Arc edge at 6'] at 12 ounces and leverage your cocoon hoody which would get you down to 26 degrees, but let's just say 32 because were not all 20 years old and have optimal conditions. The potential savings is about 7-8 ounces. You also get the added benefit to use your quilt around a sleeping bag creating a great layering system for even colder weather. e.g. 32 degree bag + 40 degree quilt = ????

Now, here's the catch. I have not actually tested this myself so this is *not* based upon experience, but rather on reading way too many forum posts. Perhaps my logic is flawed, but it seems to make sense to me.

As of *today*, if I were to need a 32 degree comfort rating for 3 season backpacking, I would get a 40 degree quilt and pair it with a cocoon hoody. Anyone disagree?

Here are my pro/cons

Quilt
+ easier to get into bivy
+ not wasting insulation being compressed on back
+ utilize hood in existing insulation to serve as sleeping hood
+ allows use of existing insulation thus allowing you to get a lighter bag and pairing it with existing insulation
+ can be used with sleeping bag to increase temp rating for colder weather.
+ easier to adjust temperature by allowing in air when warm
+ for those that do not always sleep on their bag, easier to turn with seperate hat + quilt without condensation build up
– no hood and need to wear hat
– potential drafts

Bag
+ no drafts
+ full zip bags can be unzipped and used "like" a quilt on hot days
– heavier than quilt+insulation layer quilt
– wasted insulation on back
* half zip bags are not as versatile

Following this thread, I'm struck how quilt devotees (of which I am not one) keep forgetting that most mummy style bags can be used just like a quilt. In fact, if you wanted unlimited versatility, you could just add a couple of adjustable straps to the side of you mummy bag and call it a convertible quilt.

I live and hike where there is absolutely no predicatbility to the weather and season is almost irrelevant. All my clothes are potentially part of my sleeping system (including down jacket and hood) if it gets cold enough. So I can't see how I would be better off carrying a Quilt that will keep me warm down to 20 WITH hood and Jacket on, compared to a mummy bag that will keep me warm without the extra clothes, especially when I can always open the zip of the bag and use as a quilt. With the bag, I still have a down jacket and hood in reserve if things should unexpectedly drop to 10 degrees.

In the end I agree it comes down to sleeping style, but when faced with the possibility of 4 seasons in one day, without warning, the bag will win hands down for me every time.

> I'm struck how quilt devotees (of which I am not one) keep forgetting that most mummy style bags can be used just like a quilt.
This may be a little unfair. Many quilt devotees started exactly this way.

> So I can't see how I would be better off carrying a Quilt that will keep me warm down to 20 WITH hood and Jacket on, compared to a mummy bag that will keep me warm without the extra clothes, especially when I can always open the zip of the bag and use as a quilt.
Here I think you may be misunderstanding things a bit. A sleeping bag, especially a mummy bag, almost inevitably tends to be stretched around your body. This reduces the loft. When used as a quilt it is not stretched, and in my experience at least this means it has more loft. So, in my experience, weight for weight, a quilt (or a sleeping bag used as a quilt) is warmer than the same weight of sleeping bag used as a conventional bag.

The Arc quilt is 55" at the shoulder, a standard "bag is 59-62 inches at the shoulder. A good bag will also have a differential cut. So how could it be tighter, when used as a quilt, than a purpose built quilt that is at least 4 inches narrower?

I wouldn't really be discussing the point if I hadn't been there, done that, and found a quilt of the same weight as my WM Ultralite used as a quilt (at 59 inch shoulder) just wasn't as warm, no matter how I configured it. The ability to shake most of the down into the top of something like the Ultralite also allows extra top loft when zipped up in extra cold weather. So both in theroy and in practice, the quilt just doesn't work as well for me.

Personal preference, however, is something you can't put a price on, and I think the quality quilt makers will still have plenty of business in future due to this alone. I don't think you can justify it with numbers, oz of fill, add-ons or anything more than personal preference. Sleeping style affects personal preference a lot, so a side sleeper may just plain prefer to wear a separate hood, for instance.

I tried using a couple of different mummy bags on different nights (approximately 10 times total) as quilts during the Maryland shoulder seasons (30-40 degree weather). In each case, I was quite significanly colder in the quilt, but also a lot more comfortable. When I tucked the quilt under me really well I was almost as warm as in a bag -…at least until I moved around enough for the quilt to untuck. Then I was cold enough again that it woke me up.

I typically sleep on my side in a semi-fetal position and must move around a bit, since I had to re-tuck the quilt under me about every hour when it was cold. Sleeping in a mummy bag is constraining enough that I usually only get very light sleep – even when I use a "long" bag for the extra girth. Thus, I usually don't harly sleep at all the first 2-3 days of most hikes… Alternatively, I found I got very deep sleep using the quilt – as long as I wasn't cold. I'm thinking a really thick quilt may keep me warm AND allow me to sleep unconstrained.

In all the test cases, I slept in my SD lightning double wall tent, 100 weight fleece top & long johns, mid-weight thorlo socks, acrylic knit hat and on a 2" thermarest pad. My 20 degree Sierra Designs Polarguard 3-D bag kept me warm when being used as a quilt to about 50 degrees (45 with my 200 weight fleece vest added). The same bag kept me warm to 45 degrees when being used as a bag (40 with my 200 weight fleece added). Adding my windsuit top & bottoms added another 5 degrees to each set up.

I typically only need the 100 weight fleece top + long johns, 200 weight vest, mid-weight thorlo socks, microfiber windsuit and acrylic knit hat during 3 season trips. A tiny bit more upper body insulation (ie: trade the fleece vest for a polarguard vest) would be nice sometimes in the evenings when sitting around camp cooking or eating – but carrying more would be useless except for sleeping.

I'm still searching for the smallest sleeping system that will keep me warm and have enough room to allow me to sleep. My pack volume is way too big… So I'm debating on whether to buy a 15 degree down bag, or a 5 degree quilt. Anyone know which one would pack smaller – or have any advice ?

Living in Texas I do quite a bit of Wintertime backpacking … Winter in the Houston Austin area typically never gets below 20 degrees, and usually not below 30 degrees.

Based on this I typically use a custom 25 degree quilt or a Montbell number 3 SSDH bag. Often, however, I find myself inexplicably cold some nights and warm other nights, even though there's not a significant difference in temperature.

Here's what I've found. Realitive humidity can be a sticky problem when determining temperature rating for a bag during "shoulder" seasons.

For example …. weekend before last I got very cold in my 25 degree sleep quilt with all my clothes on and in my Bivy. The temps dropped to a low of 27 degrees, and I've used this same system down to the mid 20's and been toasty warm.

This particular night the dew point was 27 degrees. As the temperature drops and approaches the dew point, the relative humidity increases and will approach 100% (fog). This is what happens when you have fog …. the temperature is just above the dew point.

When you have high relative humidity the air "feels" colder, mainly because the moisture in the air transfers heat away from your body at a faster rate.

In your sleeping bag/quilt, it's been known for years that you can reach dew point inside your insulation when it's cold outside, and result in frozen insulation.

Well, when you have high realitive humidity outside of your bag the water vapor from your body passes through your insulation at a much slower rate, resulting in higher humidity in your bag. This extra moisture has the net effect of increasing the rate of heat transfer through your insulation, as well as making the air within your bag feel "clammy".

This can have a dramatic effect on your comfort level making you colder than you would be at a lower humidity level.

As an interesting aside, once the temperature hit it's low point at about 4am, the dew condensed out of the air. The was obvious as the moisture flash froze to the outside of my bivy as well as the grass surrounding us. After the temperature hit the dew point I was able to get warm and sleep comfortably for the rest of the night with NO changes to my sleep system.

For this reason …. you should take humidity effects into account when you plan the amount of insulation you are carrying or plan on sleeping inside a tent when right around the temp limits of your sleep system.

> The Arc quilt is 55" at the shoulder, a standard "bag is 59-62 inches at the shoulder. A good bag will also have a differential cut. So how could it be tighter, when used as a quilt, than a purpose built quilt that is at least 4 inches narrower?

Ah – good question.
Me, I make my own gear, including my own SB/quilt. I can speak with confidence about my gear, but I don't know the Arc, or the others.

"Quilt
+ easier to get into bivy
+ not wasting insulation being compressed on back
+ utilize hood in existing insulation to serve as sleeping hood
+ allows use of existing insulation thus allowing you to get a lighter bag and pairing it with existing insulation
+ can be used with sleeping bag to increase temp rating for colder weather.
+ easier to adjust temperature by allowing in air when warm
+ for those that do not always sleep on their bag, easier to turn with seperate hat + quilt without condensation build up
– no hood and need to wear hat
– potential drafts

Bag
+ no drafts
+ full zip bags can be unzipped and used "like" a quilt on hot days
– heavier than quilt+insulation layer quilt
– wasted insulation on back
* half zip bags are not as versatile"

This is a good list, only I would add/modify a couple points:

Quilts
+can be tightened closer to body to minimize internal air space and thus heat more quickly/efficiently
-no hood and need to wear either a hooded jacket or layered balaclavas or an insulated balaclava, all of which add some weight compared to a mummy bag and a non-hooded jacket
-potential for drafts, which can be minimized by using a bivy bag, which adds weight

Bags
+can be used without a bivy unless using an under-sized tarp in rainy weather (example: in the desert, in most seasons you can pretty much count on it not being very rainy, so a bivy would be overkill for rain-splash protection alone and since sleeping bags zip up, you certainly don't need a bivy to stop drafts)
+side sleepers need not worry about cold drafts when they turn over in a bag
-side sleepers do need to re-adjust the mummy bag head hole when they turn over so they're not breathing directly ino the insulation for half the night
-most any bag, especially one with a hood, is overkill in heat of the summer in regions where the lows stay above 60 for most of the night

Overall, this dilemma has frustrated me recently when I decided to make a few MYOG quilts. I'm a side sleeper so I'm not using the argument, "the bottom insulation in a bag gets compressed." That simply doesn't apply to me since I have only successfully slept on my back one or two times in my life, and that was only because I was very ill at the time. With my quilt experience, I found that, *speaking for me personally*, the lack of a zipper on a quilt is downright stupid (BTW- zipers need not be heavy: a 6' length of #3 coil zipper weighs less than an ounce).

In minimizing drafts, I found that straps help–especially if you leave them long enough to go underneath a sleeping pad–but drafts still found their way in, when I was using my quilts, so I found myself making a bivy (5.5 additional ounces to my sleep system in cold weather) to minimize the drafts. What I don't really understand is that when using a synthetic quilt with, say, a momentum90 shell, what's the real need for a second layer of momentum90, the same fabric, to stop rain spash? It seems to me that the bivy in this situation would only be for drafts, but it would actually be needed to minimize drafts, compared to a sleeping bag, which doesn't need a bivy to stop drafts. Doing the math, I found that the extra weight of the bivy negates the weight savings of a quilt! That is, a 15 ounce quilt + a 5 ounce bivy weighs 20 ounces total, which is the weight of the WM Summerlite, but you still need an insulated hood for your quilt system to be comparable with the Summerlite and the hood adds even more weight.

Further, in warmer weather, *I personally* found that if I were using a quilt to stay warm, but still be comfortable, the necessary girth to use it comfortably (read: wrap it loosely around my body without the straps cinched down, and not cause me a headache every time I flip from my right side to my left side by needing to utilize prostrate acrobatics to re-position the quilt) would be 57"+ through the torso, quite a bit larger than the quilts currently being produced by companies like Nunatak, Jacks R Better and MLD, which weigh 11-15 ounces and have <48" widths through the torso. 57" is the girth of some sleeping bags, though! So why not just make the "quilt" wide enough that it can wrap around me totally, and add a very light zipper at the edges? This set up would still require an insulated balaclava or a hooded jacket for head warmth…but like I pointed out in the negative aspects of a mummy bag design: side sleepers need to perform a bit of acrobatics at night in order to re-position the face hole of a mummy bag when they turn from left to right side, so they're not breathing into the insulation. So a hoodless bag/quilt hybrid like I have described, plus an insulated balaclava, one that maintained a good neck seal, would make sense to me.

To take that one step further, the best of both worlds (again, this is *for me personally*) would be a "quilt" that's wide enough for good coverage, with a full zipper, AND some sort of strap system so I could vary the girth to minimize the internal volume of dead air space.

Edit: I just read through the most recent posts (something I should have done before typing a reply to the thread), and it seems I've repeated much of what Inaki Diaz and Allison have said. Oh well, I guess that's just further backing to those ideas.

I hear ya Roger. There's nothing like learning to make your own. Save money (in the long run) and end up with EXACTLY what YOU want based on YOUR needs. But for many folks, the time, energy and practice it takes to get to this stage is just not their cuppa tea. And the original question is a little bit different as it's comparing two sleep systems from the same manufacturer, same fill and shell, same weight, same baffle height, and same 'size". According to Nunatak's website, their Arc Bag is 61 unches "girth", same overall weight (fill and total +/- 15 grams)and same overall temp rating as their 55 inch girth Arc Quilt of the same length. I think this, more than anything else, is the conundrum. With those kinds of specs, why wouldn't you choose the bag over the quilt, since you can always use the bag up-side-down as a quilt (admittedly with a hood in your face), but you can't zip up the quilt and have a bag + hood with the quilt?

My experience to date (with MYOG stuff), is in the difference between baffle 'height' and baffle 'fill'. A Baffle is just a strip of fabric that separates down chambers and allows greater 'loft'. No where on Nunatak's website does it mention 'loft' for either of the systems, which leads me to believe the Arc Bag must have a lower loft OR a lower down density than the Arc Quilt. How this relates to temp rating is anyone's guess. We're never gonna answer this question by speculating, or pushing theoretical numbers around.

John, two down bags of equal fill weight, with equal fabric and equal total weight will almost certainly take up the same space when compressed. You are the only one who can decide the whether the benefits of perceived comfort or warmth are more important to you. Whichever you choose, please keep in mind that insulating your head is almost unarguably the most important aspect in keeping warm, so if you go with a quilt, you need to match your headwear to the quilt. And also consider that, if you want to get your pack volume down, then down will be superior to all other insulation unless you sleep in a puddle or 110% humidity for weeks at a time. Perhaps you could consider upgrading at least some of your insulating clothing/beanie to down…

Must have cross-posted with Beenay's post above. All I can say is thatpretty much sums up my opinions. Since most of the down quilt makers we're talking about will do custom work, it all just comes down to

1) Working out what is right for you;
2) Communicating this to a custom quilt/bag manufacturer, and;
3) Paying for it.

>>And the original question is a little bit different as
>>it's comparing two sleep systems from the same
>>manufacturer, same fill and shell, same weight, same
>>baffle height, and same 'size".

Good point, I was mainly going for an answer to the "When a bag is better than a quilt," general idea. It seemed that it had already been established that these two products from Nunatak had the same temp rating and the same weight, but different designs, but when I read the most recent posts, I see that there is still some uncertainty on that…

Unless your body suspends itself in mid-air, there will always be a certain quantity of down and shell/liner material flattened by your body. True, when you turn over, that flattened down will regain its loft. But then another quantity of down and shell/liner will be flattened.

That's gravity for you.

In any event, everyone has their preference for whether a quilt or bag works best. I suspect that many quilt users used bags before turning to quilts, and are not without a basis for comparison of what works best — for them.

Not trying to convince anyone that their choice isn't best for them, just clarifying that there is loss of loft from down while it is flattened by the weight of a body. Only way to avoid that fact is to levitate.

Allison – With respect to the Nunatuk Arc Alpinist loft, mine measures at 3.25 inches,YMMV. I have 2oz overfill, but this is offset by the heavier Epic fabric. For me the big quilt advantage is comfort, but I consider it slightly lighter for the same level of warmth. At 27oz I've used it to around 20 degrees.
Ron